1. Field of the Invention
This invention relates to exterior double door systems for use on buildings. In particular, this invention relates to an astragal for use in such a double door system.
2. Description of Related Art
Double door systems used in buildings as exterior doors typically include a passive door and an active door. The passive door remains fixed in place while the active door is mounted for pivotal movement. The passive door can be fixed permanently in place or releasably secured in place so that it may be opened after the active door is opened. In any case, the passive door is fixed prior to closing the active door.
In these double door systems, molding commonly called an astragal is mounted on the passive door. The astragal fills in the gap between the passive door and the active door and forms an integral part of the door system. The astragal serves two main functions: to secure the passive door in place and to provide a positive stop with a weather strip for the active door. Another common function of the astragal is to provide a surface to receive door hardware, such as a strike plate.
The building industry offers many types of astragal designs. One type is all wood, another type is all aluminum, and a third type is a combination of aluminum and wood.
The all wood design is low cost and easily installed. The wood surface also allows an installer a great deal of flexibility to accept various types of door hardware. However, wood is a weak building material compared to metal and requires a great deal of maintenance to protect it from decay.
All aluminum astragals are strong and lightweight and provide a maintenance free exterior. These astragals are easily able to withstand the stresses of normal use of an exterior door. However, aluminum is significantly more expensive than wood and does not provide any insulation, which is critical in exterior installations. Additionally, aluminum moldings typically have preset fastening formations, such as predrilled holes, so that a limited number of hardware options are available to an installer. Further, use of a dead bolt requires boring into the passive door as the aluminum astragal does not have the depth to accept the full throw of a dead bolt latch.
In an effort to use the advantages of each of these known designs, the building industry has combined aluminum and wood astragals. Typically, a wooden body is clad with an aluminum cover. The combination design lowers the cost, as less aluminum is required, and offers flexibility to accept alternate door hardware to attach to the wooden body. The drawback of this design is poor performance and durability. The wooden body is weakened when machined to receive the attachment fastener, typically a bolt or screw. The remaining wood piece offers minimal structural support and easily breaks under the stresses of normal use.
There is a need to provide a strong, durable astragal that is usable in a variety of installations and offers flexibility with respect to hardware installation.